1. Field of Industrial Utilization
The present invention relates to a method of vacuum-laminating a film-like adhesive on an inner-layer circuit pattern in a method of manufacturing a multilayered printed wiring board of a build-up system in which conductive circuit layers and insulating layers are alternately piled up.
2. Prior Art
In a known conventional method of manufacturing a multilayered printed wiring board, several prepreg sheets formed by impregnating glass cloth with epoxy resin in stage B are laminated/pressed as insulating adhesive layers on an inner-layer circuit board with a circuit formed thereon, and the layers are connected via through holes. In the method, however, since heating and pressure molding are performed during the laminating/pressing, a large scale equipment and a long time are required, which increases cost. Additionally, since the glass cloth having a relatively high permittivity is used in the prepreg sheet, reduction of interlayer thickness is limited. Another problem is that uncertainty of insulation is caused by migration among the through holes (CAF).
To solve the problem, recently technique for manufacturing a multilayered printed wiring board of a build-up system by alternately piling up organic insulating layers on conductive layers of an inner-layer circuit board has been noted. In Japanese Patent Application Laid-open No. 64960/1996, there is provided a method of applying an undercoat adhesive, tentatively drying, laminating a film-like additive adhesive, heating and hardening, roughing with alkaline oxidizing agent, and forming a conductive layer by plating to manufacture a multilayered printed wiring board. Moreover, in Japanese Patent Application Laid-open No. 202418/1995, there is disclosed a method of laminating, on an inner-layer circuit board, an adhesive copper foil obtained by forming an adhesive layer of polymeric epoxy resin and liquid epoxy resin on a copper foil to manufacture a multilayered printed wiring board. On the other hand, in Japanese Patent Application Laid-open No. 97927/1999, the present inventors have disclosed an interlayer adhesive film for a multilayered printed wiring board and a productive method of manufacturing the multilayered printed wiring board using the interlayer adhesive film, in which coating of an inner-layer circuit pattern and filling of surface via holes and/or through holes with resin can be performed simultaneously. When the adhesive films are vacuum-laminated under heating and pressurizing conditions, there is a problem that the adhesive bleeds from end portions of the adhesive films to soil press surfaces, because the adhesive is provided with thermal fluidity. To solve the problem, in Japanese Patent Application Laid-open No. 97927/1999, there is proposed a method of providing about 5 mm or more of a support base film portion with no resin on both ends or one end of the adhesive film to prevent the adhesive from bleeding. This method, however, has a disadvantage that the productivity in manufacturing the adhesive films is deteriorated.